Synthetic polyester yarns have been known and used commercially for several decades, having been first suggested by W. H. Carothers, U.S. Pat. No. 2,071,251, and then by Whinfield and Dickson, U.S. Pat. No. 2,465,319. In order to obtain polyester filamentary materials that have properties that enable them to be used in fabric construction, e.g. by knitting or weaving, it was originally thought necessary to subject the melt-spun (extruded) solid filaments to a drawing operation to increase their orientation and crystallinity. Although, in the 1950's, Hebeler, U.S. Pat. No. 2,604,667, suggested that it was possible to eliminate the drawing stage by winding up undrawn filaments at a high withdrawal speed (at least 5,200 ypm), decades passed before significant further progress was achieved towards commercial adoption of high speed spinning without requiring drawing. Essentially two techniques are now available. Knox, U.S. Pat. No. 4,156,071, discloses filamentary materials that are both crystalline and highly oriented, as defined therein, and such filaments have been prepared by spinning at withdrawal speeds of the order of 4 km/min (about 3.4 to 4.6 km/min). Frankfort and Knox, U.S. Pat. Nos. 4,134,882 and 4,195,051, disclose how to overcome difficulties in preparing filaments at the higher withdrawal speeds earlier suggested by Hebeler and the properties of the resulting new filaments. The present invention concerns the improvement of both these types of crystalline spin-oriented filamentary materials, it being understood that the present invention is not limited to operation only in the precise circumstances disclosed by the above patentees, and that there have been several disclosures of spinning crystalline spin-oriented filaments at such and higher withdrawal speeds. Although it is possible to use most such crystalline spin-oriented filaments directly in fabric construction without further drawing, it may prove advantageous to draw such filaments for certain purposes, as disclosed for example in copending application Ser. No. 07/338,251, filed Apr. 14, 1989, by Knox and Noe, and this will change the properties of the materials in certain respects that may be advantageous.
Polyester multi-filament yarn has been recognized as having significant advantages over cotton yarns in some respects, for instance its thermoplastic characteristics that enable polyester-containing fabrics to hold their shape, for instance a crease, and to have wash-wear characteristics, its low cost of manufacture, its uniformity, its superior strength, and its resistance to degradation. However, hitherto, some people have expressed a preference for wearing garments from cotton fibers because of attributes that can be summarized as "comfort", to the extent that there has been a trend recently towards using more 100% cotton fabrics, despite the practical advantages of wash-wear 100% polyester fabrics. Because of the sophistication of the textile industry, both of the polyester fiber manufacturing industry and of downstream consumers of textiles, and because of the commercial interest in providing apparel and fabrics that will perform well during actual use by the ultimate consumer (wearer), much attention has been devoted to analyzing appropriate requirements. Many technical papers, for example, have been published on various aspects, and patents have been issued with the objective of improving the "comfort" that can be obtained from textile articles, and their constituents, and the literature has been replete with these suggestions for several years. So it has long been considered desirable to improve various properties of textiles prepared from polyester yarns, and much effort has been devoted in the textile industry towards this objective.
An important objective of our invention is to provide crystalline polyester spin-oriented filaments and yarns, as mentioned above, in a new form, which can be formed into fabrics and garments that can show improved moisture-wicking properties, as discussed herein.
Polyester filaments are characterized by their extreme hydrophobic character, as mentioned in "Polyester Fibres--Chemistry and Technology", by H. Ludewig--English translation 1971--John Wiley and Sons, Ltd., in Section 11.1.5 on pages 377-378, and also in Section 11.4 on dyeing properties, starting on page 398. Indeed, the difficulty of dyeing polyester yarns and fabrics is notorious. Ludewig's book mentions many aspects of polyester fibers and their preparation and properties.
Polyester filaments are always manufactured by melt-spinning (i.e. extruding molten polyester polymer). Crystalline spin-oriented filaments are withdrawn at high speeds, as mentioned above, and are stable to storage and heat (like drawn polyester yarns), so that they can be processed without difficulty, even at elevated temperatures, e.g. of the order of 200.degree. C., if desired. In this respect, crystalline yarns are entirely different from amorphous yarns that used to be prepared at lower speeds (such as 1 km/min.) which often stick to heaters, and lose strength and break.
It is conventional to coat all freshly-extruded filaments with a "finish", which is generally an aqueous emulsion comprising a lubricant and an antistat. Finishes are discussed briefly in Section 5.5, starting on page 193, of Ludewig, referred to above. As mentioned on page 195, the literature reveals relatively little about the compositions of the spin-finishes that are actually used. Although there is now considerable patent and other literature, the precise finish formulations are generally closely-guarded secrets by the yarn manufacturers, and different compositions are formulated for different purposes, depending on the particular intended processing and possible specific requests by individual customers, and these formulations change, sometimes quite frequently. As will be related hereinafter, a dramatic change in the surface properties of the filaments, and of articles containing them, such as fabrics and garments, may be obtained by a relatively simple modification to the spin-finish that is applied to the freshly-extruded polyester crystalline spin-oriented filaments. Conventionally, the spin-finish is the first contact that a freshly-extruded filament encounters after solidification. The finish was generally applied by a finish roll, rotating in a bath of the finish, so that the filaments pass through the finish emulsion as they brush past the finish roll on their way from the solidification zone to the feed roll that determines the withdrawal speed from the spinneret. Before the finish roll, it is generally desirable to avoid or minimize contact between the filaments and solid objects, and so the only other closely-adjoining solid objects are generally guides that are intended to confine the filaments before contacting the finish roll. A finish roll is not the only method of applying finish, and other methods have been used and suggested, including spraying or metering the finish onto the filaments.